Mobile communication systems include any ad hoc network system, without requiring any existing infrastructure as typified by a server, an exchange, and a base station, where a mobile communication device finds a communication path by itself, and uses the found communication path to communicate with another mobile communication device.
In conventional ad hoc network systems, a tentative master device is determined from among a plurality of mobile communication devices that are operable to serve as both a master device and a slave device, and the other mobile communication devices are determined as slave devices. In such a state, when data exchange between the master device and the slave devices is enabled, a transfer rate measured by using a test signal, and the residual power of a storage battery of each slave device are transmitted from the slave device to the master device. The master device reselects a true master device based on each transfer rate and each residual power collected in a manner as described above.